It is well known to provide liquid fabric conditioning compositions which soften in the rinse cycle.
Such compositions comprise less than 7.5% by weight of softening active, in which case the composition is defined as “dilute”, from 7.5% to about 30% by weight of active in which case the compositions are defined as “concentrated” or more than about 30% by weight of active, in which case the composition is defined as “super-concentrated”.
Concentrated and super-concentrated compositions are desirable since these require less packaging and are therefore environmentally more compatible than dilute or semi-dilute compositions.
A problem frequently associated with concentrated and superconcentrated compositions, as defined above, is that the product is not stable upon storage, especially when stored at high temperatures. Instability can manifest itself as a thickening of the product upon storage, even to the point that the product is no longer pourable.
The problem of thickening upon storage is particularly apparent in concentrated and superconcentrated fabric softening compositions comprising an ester-linked quaternary ammonium fabric softening material having one or more fully saturated alkyl chains.
However, it is desirable to use ester-linked compounds due to their inherent biodegradability and to use substantially fully saturated quaternary ammonium fabric softening compounds due to their excellent softening capabilities and because they are more stable to oxidative degradation (which can lead to malodour generation) than partially saturated or fully unsaturated quaternary ammonium softening compounds.
Of the types of ester-linked quaternary ammonium materials known, it is desirable to use those based on triethanolamine which produce at least some mono-ester linked component and at least some tri-ester linked component since the raw material has a low melting temperature which enables the manufacturing process of the composition to occur at low temperatures. This reduces difficulties associated with high temperature handling, transport and processing of the raw material and compositions produced therefrom.
Certain of the abovementioned problems have previously been addressed. For instance, it is known to inhibit thickening of concentrated and superconcentrated compositions by providing an electrolyte within the composition. However, electrolytes are known to have a destabilising influence on such compositions upon storage.
it has also been proposed in WO-A1-95/16766 to provide a stable highly concentrated fabric conditioning composition containing a mixed active system. A first component of the active system has an iodine value of less than 10 and a second component has an iodine value of from 20 to 100. On page 4 of the description, it is clearly stated that the first component must be at least 80% diester and less than 20% monoester. Furthermore, on page 2 it is taught that the second component is a structurally different material from the first component. This document only teaches that the presence of an unsaturated component enables formulation of fabric conditioning compositions having a higher concentration.
There is no teaching nor any disclosure of optimising the mono-ester content of the unsaturated component to further improve stability of highly concentrated compositions.
Furthermore, by introducing high levels of unsaturation into the formulation, the product can become liable to oxidative degradation, leading to rancid or fatty malodours forming on storage—particularly at high temperatures.
U.S. Pat. No. 4,439,335 discloses mixtures of quaternary ammonium materials, one of which is a di(amidoethyl)methyl quaternary ammonium salt and/or imidazolinium salt.
U.S. Pat. No. 5,501,806 also discloses mixtures of softening actives to achieve highly stable, highly concentrated systems. It discloses mixtures of components A and B at a total level of 25 to 50% by weight of active ingredient). In all examples and the claims, A is a mineral or organic acid salt of an amidoamine.
U.S. Pat. No. 4,963,274 discloses concentrated formulations comprising mixtures of active ingredients.
EP-B1-0593542 discloses on page 4 line 51 a mixture of Tetranyl AHT-1 and Tetranyl AT-1 in a ratio of 4:1. The combined mixture is present in an amount of 5% by weight.
Surprisingly, we have now found that a highly concentrated softening composition in which saturated and unsaturated softening species based on triethanolamine are present and in which the level of the softening components of the saturated species in the formulation (particularly the hardened di- and tri-esters components) are maximised whilst the amount of unsaturated species present is optimised to within a specific range provides excellent softening performance, reduced product malodour generation and reduced instability.
The disclosure of a mixture of saturated and unsaturated species in the prior art does not identify nor even suggest that by optimising the monoester species of the unsaturated material to within a particular range, significant benefits in terms of stability without loss of softening and odour control can be achieved.